Large Export Issues - QGIS 3.2.2

Question

Still pretty new to GIS, but Ive been working on assembling a map with ~20 vector layers over the past couple of weeks. Its finally to a point where Im ready to export. Ive been experimenting with various export methods for a few days now, and I cant seem to get what Im looking for.

Map info - its massive, covers over a million acres. my goal is to have it printed on a banner, 10 feet wide, by however tall makes sense to preserve the aspect ratio For prints of this size, DPI needs to be high, ~300 or more, from what Ive read Scale - Im trying to keep it around 1:24000, or even 1:20000

I have been trying for either a PDF or a TIF file.

When I use the exact settings I want, the export fails with one of those errors about it being too big, cant allocate enough memory, ect.

This happens for both the Project -> export, and the print composer methods.

When I tweak the settings, compromising on either scale, or dpi, I eventually get a successful output, kind of. The files it creates look clean, open up fine, but they have part of map cut off, always the far right edge. And sometimes there is even a strange black block that appears in the area that was cutoff. It seems as though the exporting process works left to right across my map, and fails at some point, but doesnt report it as a failure.

Below is an example of what Im talking about, Ive stacked 3 different export attempts, with my full QGIS map on the top (please ignore the label mess):

Any suggestions for what else I might try?

Answer 1

Since you managed to export in 3 sections successfully and the only remaining problem is that the labels don't line up, I have two suggestions. Let me know if either of them works.

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First method - easier, but not guaranteed to work.

Export in sections from the map canvas.

First try this:

• Zoom map canvas to the entire extent of the map. Export from this extent. Hopefully the labels won't change places between sections.

If the labels don't line up between sections, try this:

• Zoom in to the scale that you want the export to be at (1:24000 or 1:20000). Use the Magnifier to zoom out until you can see the entire extent again. Export in sections as before.

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Second method - more time consuming, but will probably work.

Export in sections without labels. Export the labels separately. Combine in a program like scribus or acrobat pro.

To create the export with only labels:

1. Duplicate every layer that has labels.

   • In layer panel, right click on the layer name > Duplicate Layer

2. Copy the style from the original layer, and paste it onto the duplicate.

   • In layer panel, right click on the original layer name > Styles > Copy style.
   • In layer panel, right click on the duplicate layer name > Styles > Paste style.

3. Put all the duplicate layers in a group to make it easy to keep track of them.

4. Change the symbology of each duplicate layer to "No symbols."

5. In print composer, right click on the page > page properties > background > set opacity to 0%.

6. Turn off all the other layers, and export from print composer in a single section.

Because the labels-only map is much less detailed than the entire map, hopefully it won't require too much memory to export as one section. If this doesn't work, you could try exporting at a slightly lower dpi, and just have slightly blurry labels. Or try exporting with only the labels from one or two layers at a time, then combine them in the final product. This may lead to overlapping labels, but you should be able to rearrange them manually in the final product.

Finish by exporting the rest of the map in sections without labels. Combine in a program like Scribus or Acrobat Pro.